In order to determine the serotype specificity of rotaviruses, an assay based on the use of genetic probes to recognize specific areas of the VP4 and VP7 genes was developed using the polymerase chain reaction (PCR). The assay consists of selectively amplifying (with the use of specific primers) highly divergent regions of the VP4 or VP7 genes associated with neutralization specificity. By incorporating p32-deoxy ATP high specific activity probes were generated and hybridization of the probes to RNAs from rotavirus positive stool suspensions or infected tissue culture lysates was used to identify serotype.